This invention relates to vehicle bumper energy absorbers used on vehicles within the automotive and light truck market, and will allow for a totally integrated bumper system providing both energy absorption and structural integrity, as well as a core for which to mount a vehicle""s fascia.
Substantially all vehicle bumper systems are designed to serve several functions, one of which is to minimize damage to the vehicle body during low speed impacts (typically defined as less than 5 miles per hour), another is to manage the energy resulting from the impact. A properly designed bumper system will withstand these low speed impacts with no or minimal damage to the bumper system or to other vehicle components. A properly designed bumper system will repeatably manage the energy during these low speed impacts without permanent damage to the bumper system or to other vehicle components.
A goal of generally any bumper system is to provide a design that is lightweight and has the ability to manage kinetic energy created during bumper impact incidents, as indicated above. The bumper system must also be designed for strength and be resistant to excessive torsion and flexing.
A well designed bumper system will allow for full bumper fascia support and optimal cross sectional areas adequate to meet the vehicle off-set (allowable stroke) requirements, while minimizing material usage, and, at the same time, reducing total system weight. It is also desirable to minimize the use of bumper system fasteners and/or adhesives used in the assembly of these systems.
The present invention meets the above mentioned requirements and provides a high performance bumper energy management system, while incorporating a simple, preferably single step, commercial manufacturing process, and, at the same time, reduces the number of components to reduce the cost of assembly.
There are a number of related patents that deal peripherally with the present invention. For example, U.S. Pat. No. 5,255,487 (Wieting et al.) discloses a door reinforcement beam for use in a passenger vehicle which includes a base tube made of a metal and a reinforcing section attached to the tube which is also made of a metal.
U.S. Pat. No. 5,884,960 (Wycech) discloses a reinforced door beam that has a hollow shell within an internal localized reinforcement. The localized internal reinforcement includes an inner shell which is spaced apart from the door beam shell by a layer of thermally expanded resin.
U.S. Pat. No. 5,992,923 (Wycech) discloses a reinforced beam assembly that includes a channel shaped beam which has an internal reinforcement member located within the channel. The reinforcement member is of a W-shape and functions as a carrier for an expandable foam located between the inner and outer surface of the reinforcement member and the inner surface of the beam. Upon expansion, the foam is bonded to both surfaces.
U.S. Pat. No. 6,003,274 (Wycech) discloses a lightweight structural reinforcement that spans a space in a structural member. The reinforcement functions as a web and has a metal plate, a layer of foam, and a thin, metal reinforcement selectively positioned at the midportion of the reinforcement. Unexpanded foam at the end portions of the plate serves as an adhesive to bond the reinforcement to the structural member being reinforced.
U.S. Pat. No. 6,092,864 (Wycech et al.) discloses a laminate for reinforcing a structural member having side walls. The laminate has a carrier having at least one inclined support surface. Each support surface has an outer edge disposed toward a respective side wall. A layer of extruded, uncured structural foam is on each support surface and terminates inwardly off the outer edge. The foam expands when cured and tumbles down the inclined support surface of the carrier to become bonded to the side wall as well as the carrier.
U.S. Pat. No. 6,168,226 (Wycech) discloses a laminate support beam that includes an outer structural member which has a channel shape with a longitudinal rigid inner member precoated with structural foam to form a drop-in insert unit which is dropped into the channel of the outer structural member. The structural foam is heat expandable to intimately bond to the inner surface of the outer member and provide a reinforcement for the outer member.
U.S. Pat. No. 6,199,940 (Hopton et al.) discloses a reinforcing member for receiving thereon a thermally expansible reinforcing material. The member includes a tubular carrier and a fastener mechanically affixing the reinforcing material to the carrier. The tubular carrier has a continuous arcuate wall with the reinforcing material received on the exterior thereof. The reinforcing material may be provided as a plurality of longitudinally spaced annular elements, an elongated sleeve, or a plurality of prism-shaped elements. Upon heating, the reinforcing material expands and bonds the carrier to the structural member to provide additional strength and stiffness.
U.S. Pat. No. 6,233,836 (Wycech) discloses a method for reinforcing a selected portion of a structural part which utilizes a flexible tube having an unexpanded, thermally expandable resin sheath. The sheath may be limited to a selected region along the length of the flexible tube. The flexible tube is inserted through a curved passage and conforms to the geometry of the part to be reinforced. After the portion of the tube having the sheath reaches the desired location, the tube is secured in place. Upon heating, the resin expands to several times its original volume and fills the structural cavity only at that region.
U.S. Pat. No. 6,305,135 (Hopton et al.) discloses a reinforcing member for a structural component such as a rail or channel of a vehicle which includes a carrier and a thermally expansible structural reinforcing material element which is fastened to the carrier by mechanical fixation or an adhesive. The mechanical fixation may be provided by a flange or other mechanical connection on the carrier or by a fastener such as a push pin extending through aligned holes and openings in the carrier and foamable material. The push pins are of a synthetic resin material which more closely approximates the heat conductivity of the foamable material when they are activated by heat, and are sufficiently yieldable to absorb impacts to the foamable material during installation.
Finally, U.S. Pat. No. 4,456,443 (Rabotski) discloses a steam chest molding process in general, wherein articles such as foamed boards or sheets are molded from expanded foam material, such as polystyrene. A cavity is filled with beads of partially expanded polystyrene and steam is used to completely expand the beads. The foam is then cooled with water.
All references cited herein are incorporated herein by reference in their entireties.
The present invention is directed to a one-piece vehicle bumper energy absorber system containing a densified molded foam and at least one bumper beam reinforcing member. During a low speed impact (5 miles per hour or less), upon impact, as the densified molded bead foam compresses within or around the reinforcing member, it will partially absorb the kinetic energy of the impact, thus reducing the abruptness of the initial impact. The reinforcing member minimizes any torsional forces, allows for adequate energy absorption, and prevents damage to the vehicle body and related components.
Once the initial impact occurs, and after the kinetic energy is absorbed and the impactor is removed, the bumper system rebounds to its normal free state. This rebound results from the stiffness of the bead foam in conjunction with the reinforcing member.
Upon the initial vehicle impact, which results in deformation of the bead foam and the transmission of the compressive forces, the system will distribute the load throughout the bumper system and into the frame of the vehicle. It is the systematic balance of the energy absorption rate and subsequent transfer of energy within the vehicle that minimizes any damage to the body of the vehicle.
The present invention is directed to a vehicle bumper energy absorbing system that includes molded foam and an integral reinforcing member. The molded foam at least partially encapsulates the reinforcing member. The molded beam foam is adapted to absorb impact energy and distribute impact forces to the reinforcing member. The reinforcing member may be of a plate shape. Fasteners are preferably used to enable the vehicle bumper energy absorbing system to be mounted to a vehicle frame. Preferably, the fasteners are integral to the molded bead foam or integral to the reinforcing member. Preferably, the vehicle bumper energy absorbing system is adapted to be manufactured in a single step process, wherein the thermoplastic bead foam encapsulates the reinforcing member.
The reinforcing member may be, for example, a stamped plate, a rolled beam, an extruded shaped beam, or a molded beam or plate. The reinforcing member may be, for example, stamped metal, a plastic beam, or a thermoformed beam comprised of metal or a composite blend.
Optionally, the reinforcing member may contain holes (including slots) where the molded bead foam has passed through. The reinforcing member may have barbs on one or more outer surface for enhanced securement of the molded bead foam to the reinforcing member. The length of the reinforcing member may range, for example, from 50 mm to 1000 mm as measured from the centerline of the vehicle bodyline.
Optionally, a fascia layer is located adjacent to at least one surface of the bumper energy absorbing system. The fascia is integral to the bumper energy absorbing system.
A method of making a vehicle energy absorbing system is also provided which generally includes the steps of providing a pair of mold halves that close to form a mold cavity adapted to be used in a steam chest molding process, providing a reinforcing member into the mold cavity, applying foam beads into the mold cavity such that the reinforcing member is encapsulated by the foam on at least one side, and densifying the foam beads within the mold cavity. The reinforcing member may be temporarily positioned within the mold cavity to allow the bead foam to be injected around or within it. The step of densifying the foam beads within the mold cavity may include utilizing mechanical pressure through the use of a telescoped mold cavity. The step of densifying the foam beads within the mold cavity may also include utilizing air pressure through the use of a pressurized air within the range of 0.5 bar to 5.0 bar. This process is commonly referred to as xe2x80x98pressure fillxe2x80x99 technology within the industry.
A compression chest molding technique may also be used preferably including injecting high pressure steam within the range of, e.g., 1.5 to 5.5 bar into the mold cavity through vents contained within the mold cavity subsequent to the step of applying foam beads into the mold cavity. This is a steam chest molding technique, wherein high pressure steam (within the range of, e.g., 1.5 to 8.0 bar) is injected into the mold cavity through vents contained within the mold cavity. These mold cavity vents (referred to as xe2x80x98core-ventsxe2x80x99) may be present on one or both sides of the mold cavities.
The step of providing the pair of mold halves may include providing a single molding tool containing multiple mold cavities. The step of densifying the foam beads may include densifying the foam beads to a final foam density of, for example, between about 20 grams/liter and 350 grams/liter or about 15 grams/liter and 300 grams/liter. The step of densifying the foam beads may include densifying the foam beads to a plurality of foam densities within the same part. A step of cooling the mold halves may be used to facilitate proper annealing of the expanded bead foam in and/or around the reinforcing member.
The method may include the step of applying a fascia to at least one surface of the foam beads within the mold. Preferably, the steps of providing the pair of mold halves, providing the reinforcing member into the mold cavity, applying foam beads into the mold cavity, and densifying the foam beads within the mold cavity all occur in a single molding operation. Alternatively, the steps of providing the pair of mold halves, providing the reinforcing member into the mold cavity, applying foam beads into the mold cavity, densifying the foam beads within the mold cavity, and applying a fascia, all occur in a single molding operation.